Genotoxic activity of plant growth-regulating hormones in Aspergillus nidulans

Three plant growth-regulating hormones, indole-3-acetic acid(IAA), indole-3-butyric acid (IBA), and kinetin (6-furfuryl-aminopurine),were tested for their genetic activity in Asper-gillus nidulansin a plate test. The first two hormones were found to greatlyincrease somatic segregation in the fungus whereas kinetin wasnot effective. Several concentrations of the plant hormoneswere used and it was found that increasing concentrations ofIAA and IBA increased mitotic segregation of the fungus withmost of the segregants being produced by mitotic crossing-over,together with non-disjunctional segregants at a lower level.The metabolic activation technique was also used and it wasshown that when S9 mixture was added to IAA and IBA a further3- to 5-fold increase in the number of segregants was obtained.In the case of kinetin the S9 had no effect.